Unsaturated polyester resins from copolymers of allyl alcohol propoxylates and vinyl aromatic monomers

ABSTRACT

Copolymers of vinyl aromatic monomers and propoxylated allyl alcohols having an average of 2 or less oxypropylene groups are disclosed. The copolymers, which have hydroxyl numbers of 80-260 mg KOH/g and number average molecular weights from 500-3500, are particularly useful for polyurethanes, alkyd resins and coatings, melamine-based coatings, and unsaturated polyester resins.

This is a division of application Ser. No. 08/249,106, filed May 26,1994, now U.S. Pat. No. 5,451,631, which is a division of applicationSer. No. 08/098,114, filed Jul. 28, 1993, now U.S. Pat. No. 5,382,642.

FIELD OF THE INVENTION

The invention relates to copolymers made from vinyl aromatic monomersand low molecular weight propoxylates of allyl alcohol. The copolymers,which have hydroxyl and olefin functionalities, are resinous polyolsthat are particularly useful for polyurethanes, alkyd resins andcoatings, melamine coatings, and unsaturated polyesters.

BACKGROUND OF THE INVENTION

Allyl alcohol, which is made commercially by isomerizing propyleneoxide, is widely used to make allyl ether and allyl ester derivativesfor pharmaceuticals, fragrances, and chemical intermediates. Allylalcohol advantageously features both hydroxyl and olefin functionalgroups; however, because it is flammable and highly toxic, allyl alcoholmust be handled carefully. For many applications, propoxylated allylalcohols, i.e., reaction products of allyl alcohol and an equivalent ortwo of propylene oxide, are favorable replacements for allyl alcoholbecause they have the same functional groups (and similar reactivity),but are less volatile and less toxic.

Allyl alcohol copolymerizes with vinyl aromatic monomers such as styrene(See, for example, U.S. Pat. Nos. 2,894,938 and 2,940,946). Because ofthe large reactivity difference between the monomers, the process is runwith a large excess of allyl alcohol; unreacted allyl alcohol isrecovered by distillation and is then recycled to the polymerizationreactor. The resulting styrene/allyl alcohol copolymers are used in avariety of products, including polyesters, fatty ester emulsions, anduralkyds. The insolubility of styrene/allyl alcohol copolymers inpolyether polyols limits their usefulness in polyurethane foams.

Hult and Johansson (J. Polym. Sci., Part A, Polym. Chem. Ed. 29 (1991)9) polymerized styrene in the presence of up to 12 mole percent ofethylene glycol monoallyl ether or propylene glycol monoallyl ether, andconcluded that allyl ethers do not copolymerize with styrene, butinhibit styrene polymerization.

Copolymers of vinyl aromatic monomers and higher molecular weightpolyether polyols containing unsaturation are known. For example, U.S.Pat. No. 3,823,201 (Pizzini et al.) teaches graff copolymer dispersionsmade by reacting vinyl monomers with polyether polyols havingfunctionalities of 2 to 6, preferred equivalent weights of 250 to 5000,and unsaturations of 0.10 to 0.70 meq/g. U.S. Pat. No. 4,264,755 (Cross)teaches hydroxy-functional vinyl copolymers produced by copolymerizingstyrene with a mono- or diallyl ether of a saturated aliphatic polyolhaving a hydroxyl functionality of 3-4. The resulting copolymers havehydroxyl numbers from 45 to 100, and number average molecular weightsfrom 7,000 to 20,000.

U.S. Pat. No. 4,722,978 (Yu) teaches allyl-terminated polyethermacromonomers ("macromers"). Cationic polymerization of an epoxide orglycidyl ether in the presence of an allylic alcohol starter gives amacromer that has from 2 to 500 oxyalkylene units. The macromercopolymerizes with vinyl monomers, including styrene. New copolymersderived from allyl monomers and vinyl aromatic monomers are needed.Preferably, the copolymers would be soluble in polyether polyols, andcould be made from monomers that are volatile enough to recover from apolymerization mixture by distillation. Copolymers useful in a varietyof alkyd resin, polyurethane, and melamine-based products, especiallycoatings, would be desirable.

SUMMARY OF THE INVENTION

The invention is a copolymer of a vinyl aromatic monomer and apropoxylated allyl alcohol. The propoxylated allyl alcohol has theformula CH₂ =CH-CH₂ --(A)_(n) --OH, in which A is an oxypropylene group,and n, which is the average number of oxypropylene groups, has a valueless than or equal to 2. The vinyl aromatic/propoxylated allyl alcoholcopolymer has a hydroxyl number within the range of about 80 mg KOH/g toabout 260 mg KOH/g, and a number average molecular weight within therange of about 500 to about 3500.

The invention includes polyurethanes, alkyd resins and coatings,melamine-based coatings, and unsaturated polyester resins made from thevinyl aromatic/propoxylated allyl alcohol copolymers. The improvedsolubility of the copolymers of the invention in polyethers expandstheir usefulness in polyurethanes relative to styrene/allyl alcoholcopolymers.

Because the propoxylated allyl alcohols used in the invention have anaverage of 2 or less oxypropylene units, they are volatile enough to usein excess in copolymerizations with vinyl aromatic monomers; unreactedpropoxylated allyl alcohols are efficiently recovered by distillationand reused. This feature permits the synthesis of copolymers thatinclude up to about 50 mole percent of propoxylated allyl alcoholrecurring units.

DETAILED DESCRIPTION OF THE INVENTION

The copolymers of the invention have recurring units of a vinyl aromaticmonomer and a propoxylated allyl alcohol. Vinyl aromatic monomers usefulin the invention are aromatic compounds that have a --CH=CH₂ groupattached to an aromatic ring. Suitable vinyl aromatic monomers include,but are not limited to, styrene, alkyl-substituted styrenes (e.g.,4-methylstyrene, 4-tert-butylstyrene, 2,6-dimethylstyrene), halogenatedstyrenes (e.g., 4-chlorostyrene, dichlorostyrenes, dibromostyrenes,tribromostyrenes), vinyl naphthalenes, and the like, and mixturesthereof. A minor proportion of a di- or polyvinyl aromatic monomer suchas divinylbenzene can be included if a greater degree of crosslinking isdesired, although preferably only a monovinyl aromatic monomer is used.Styrene and halogenated styrenes are preferred vinyl aromatic monomers.

A propoxylated allyl alcohol is copolymerized with the vinyl aromaticmonomer. Suitable propoxylated allyl alcohols have the formula:

    CH.sub.2 =CH-CH.sub.2 --(A).sub.n --OH

in which A is an oxypropylene group, and n, which is the average numberof oxypropylene groups in the propoxylated allyl alcohol, has a valueless than or equal to 2. The oxypropylene groups in the propoxyatedallyl alcohols have one or both of the structures --OCH(CH₃)--CH₂ -- and--OCH₂ --CH(CH₃)--, which will depend on the method of synthesis.Suitable propoxylated allyl alcohols can be prepared by reacting allylalcohol with up to 2 equivalents of propylene oxide in the presence of abasic catalyst as described for example, in U.S. Pat. Nos. 3,268,561 and4,618,703, and J. Am. Chem. Soc. 71 (1949) 1152, the teachings of whichare incorporated by reference herein in their entirety. Suitablepropoxylated allyl alcohols can also be made by acid catalysis, asdescribed, for example, in J. Am. Chem. Soc. 71 (1949) 1152. Preferredpropoxylated allyl alcohols are those for which n has a value within therange of about 1.4 to about 1.8.

The vinyl aromatic/propoxylated allyl alcohol copolymers of theinvention have hydroxyl numbers within the range of about 80 mg KOH/g toabout 260 mg KOH/g, preferably within the range of about 100 mg KOH/g toabout 200 mg KOH/g. The number average molecular weight of thecopolymers will be within the range of about 500 to about 3500,preferably from about 1000 to about 2000. The copolymers of theinvention will typically have average hydroxyl functionalities greaterthan 2, preferably from about 2 to about 6, and more preferably fromabout 3 to about 5.

The relative amounts of vinyl aromatic monomer and propoxylated allylalcohol used to make the copolymers of the invention are not criticaland can be adjusted as desired to control physical properties. Preferredcopolymers will have at least about 10 mole percent of propoxylatedallyl alcohol recurring units. Preferably, the mole ratio of vinylaromatic monomer to propoxylated allyl alcohol recurring units is withinthe range of about 50:50 to about 90:10. A more preferred range is fromabout 60:40 to about 70:30.

The copolymers of the invention are made by copolymerizing a vinylaromatic monomer and a propoxylated allyl alcohol in the presence of afree-radical initiator. Because the vinyl aromatic monomer reacts muchfaster than the propoxylated allyl alcohol, the polymerization ispreferably performed with a large excess of the propoxylated allylalcohol; this excess is needed to give copolymers having 10-50 molepercent of propoxylated allyl alcohol recurring units.

Unreacted propoxylated allyl alcohol is recovered by any suitable means,preferably distillation, and is returned to the polymerization reactor.Thus, it is important that the propoxylated allyl alcohol have no morethan an average of two oxypropylene units so that unreacted material canbe recovered from the polymer by distillation and be reused. When theaverage number of oxypropylene units exceeds 2, unreacted propoxylatedalcohol is not easily distilled from the polymer product, andpreparation of polymers having 10-50 mole percent of propoxylated allylalcohol recurring units becomes impracticable.

In the process for preparing the vinyl aromatic/propoxylated allylalcohol copolymers of the invention, the polymerization temperature,initiator half-life, and rate of vinyl aromatic monomer addition arepreferably adjusted to minimize the concentration of unreacted vinylaromatic monomer in the reactor at any given time during thepolymerization. Thus, all of the propoxylated allyl alcohol ispreferably present in the reactor at the start of the polymerization,while most of the vinyl aromatic monomer is added gradually during thepolymerization. The vinyl aromatic monomer is added slowly enough toavoid accumulating a large concentration of vinyl aromatic monomer inthe reactor. If a faster vinyl aromatic monomer addition rate isdesired, the process can be performed at a higher temperature with asuitable initiator.

The free-radical initiator is chosen with the desired polymerizationtemperature and monomer addition rate in mind. Preferred free-radicalinitiators are peroxide and azo-type compounds that have a relativelyshort half-life at the polymerization temperature. Preferably, theinitiator half-life is within the range of about 30 seconds and about 30minutes at the polymerization temperature chosen. Those skilled in theart can select a suitable initiator by reviewing the literatureavailable from suppliers of free-radical initiators, which typicallygives the half-life at various temperatures for a given initiator.Generally, one selects an initiator that has a relatively shorthalf-life at the desired reaction temperature.

The propoxylated allyl alcohol and the vinyl aromatic monomer arecopolymerized at a temperature high enough to copolymerize the monomers,and high enough to prevent the vinyl aromatic monomer from accumulatingin the reactor. Preferred polymerization temperatures are within therange of about 100° C. to about 250° C. A more preferred range is fromabout 135° C. to about 200° C.

The invention includes polyurethanes made with the vinylaromatic/propoxylated allyl alcohol copolymers of the invention. Thecopolymers have hydroxyl functionalities and molecular weights in thesame range as polyols that are typically used in polyurethanes. Thecopolymers can thus be used in combination with or in place of ordinarypolyols in polyurethane coatings, sealants, elastomers, adhesives, andfoams (flexible, rigid, semi-rigid).

For example, a useful polyurethane coating is made by reacting astyrene/propoxylated allyl alcohol copolymer with a polyisocyanate tomake a prepolymer; the prepolymer is moisture cured or chain extended togive the coating. The styrene/propoxylated allyl alcohol copolymer isoptionally used in part or whole as the chain extender. In anotherexample, a flexible polyurethane foam is made. A copolymer of theinvention is combined with a polyether polyol to give a homogeneousmixture. The mixture is combined in a one-shot process with toluenediisocyanate, amine catalyst, tin catalyst, surfactant, and water toproduce a flexible polyurethane foam.

The invention also includes alkyd resins made with the vinylaromatic/propoxylated allyl alcohol copolymers of the invention. Thecopolymer, or a mixture of the copolymer with glycerin or another lowmolecular weight polyol, is partially esterified with an unsaturatedfatty acid to give an alkyd resin. The alkyd resin is combined with anorganic solvent, and the resin solution is stored until needed. A dryingagent such as lead acetate or cobalt acetate is added to the solution ofalkyd resin, the solution is spread onto a surface, the solventevaporates, and the resin cures leaving an alkyd coating of theinvention. Suitable unsaturated fatty acids are those known in the artas useful for alkyd resins, and include, for example, oleic acid,ricinoleic acid, linoleic acid, linolenic acid, licanic acid, and thelike, and mixtures thereof. Mixtures of unsaturated fatty acids andsaturated fatty acids such as lauric acid or palmitic acid can also beused.

Instead of combining the alkyd resin with an organic solvent, the resincan be dispersed in water to make a water-based alkyd coatingformulation. To improve the water dispersability of the alkyd resin, afree hydroxyl group in the alkyd resin can be converted to a salt. Forexample, the alkyd resin can be reacted with phthalic anhydride to givea resin that contains phthalic acid residues; addition of sodiumhydroxide makes the sodium phthalate salt, and provides awater-dispersable alkyd resin derived from the vinylaromatic/propoxylated allyl alcohol copolymer.

Alkyd resins derived from the copolymers of the invention can also beused for polyurethane coatings. For example, a styrene/propoxylatedallyl alcohol copolymer is partially esterified with an unsaturatedfatty acid to give an alkyd resin. The alkyd resin, which contains somefree hydroxyl groups, is reacted with a polyisocyanate to give aprepolymer. The prepolymer then reacts with a chain extender or more ofthe alkyd resin to give an alkyd-modified polyurethane (uralkyd)coating.

The invention includes melamine-based coatings prepared from vinylaromatic/propoxylated allyl alcohol copolymers. A copolymer of theinvention reacts with a melamine-type crosslinking agent such ascommercial grade hexamethoxymethylmelamine to give a crosslinkedcoating. Suitable melamine-type crosslinking agents include, forexample, CYMEL 303 crosslinking agent, a product of American CyanamidCompany.

The invention also includes unsaturated polyester resins prepared fromvinyl aromatic/propoxylated allyl alcohol copolymers. The copolymers ofthe invention are used in place of some or all of the glycol componentin a conventional unsaturated polyester synthesis. For example,styrene/propoxylated allyl alcohol copolymer is reacted with propyleneglycol, maleic anhydride, and phthalic anhydride to produce anunsaturated polyester resin. The resin is combined with styrene, and iscured with a free-radical initiator to give a cured, thermoset polyesterarticle.

The following examples merely illustrate the invention. Those skilled inthe art will recognize many variations that are within the spirit of theinvention and scope of the claims.

PREPARATION OF STYRENE/PROPOXYLATED ALLYL ALCOHOL COPOLYMERS Example 1

Propoxylated allyl alcohol (average mol. wt. 150, average of 1.6oxypropylene units per molecule, 1200 g) is charged to a 2-L reactionkettle equipped with an agitator, a condenser, an addition funnel, atemperature controller, and a nitrogen inlet. A solution oft-butylperbenzoate (60 g) in styrene (600 g) is charged to the additionfunnel. The reaction kettle is purged with nitrogen, and thepropoxylated allyl alcohol is heated to 135° C. Thestyrene/t-butylperbenzoate solution is gradually added over 6.5 h at135° C. After the addition is complete, the reactor is cooled to 25° C.Unreacted monomer is removed by stripping under vacuum (1 mm Hg) whilegradually heating the mixture to 250° C. The resultingstyrene/propoxylated allyl alcohol copolymer (853 g) has hydroxyl number=107 mg KOH/g, and acidity =0.002 mg KOH/g. Gel permeationchromatography (GPC) analysis of the copolymer using polypropyleneglycol standards indicates: M_(w) =3700, M_(n) =1500.

Example 2

The procedure of Example 1 is followed, except that VAZO 67 initiator(product of DuPont) 2,2'-azobis(2-methylbutyronitrile)!(60 g) is usedinstead of t-butyl-perbenzoate. The resulting styrene/propoxylated allylalcohol copolymer (764 g) contains 25.7 mole percent of recurring unitsderived from propoxylated allyl alcohol (by carbon-13 NMR analysis).Hydroxyl number: 114 mg KOH/g. Acidity: <0.001 mg KOH/g. GPC data: M_(w)=2460; M_(n) =1250.

Example 3

Preparation of Dibromostyrene/Propoxylated Allyl Alcohol Copolymer

Propoxylated allyl alcohol (as in Example 1) is charged to a 1-Lreaction kettle equipped as in Example 1. A mixture of dibromostyrene(250 g) and VAZO 67 initiator (25 g) is charged to the addition funnel.After purging the reactor with nitrogen, the propoxylated allyl alcoholis heated to 135° C., and the dibromostyrene/initiator solution is addedgradually over 6.0 h at 135° C. After the addition is complete, thereactor is cooled to 25° C. Unreacted monomer is removed by strippingunder vacuum while gradually heating the mixture to 200° C. Theresulting copolymer contains 47.4 mole percent of recurring units ofpropoxylated allyl alcohol. Hydroxyl number: 144 mg KOH/g. Acidity:0.009 mg KOH/g. GPC results: M_(w) =2040; M_(n) =900.

The preceding examples are meant only to illustrate the invention. Thescope of the invention is defined by the following claims.

I claim:
 1. An unsaturated polyester resin composition which comprisesthe reaction product of:(a) an anhydride; (b) optionally, a glycol; and(c) a copolymer which comprises recurring units of:(i) a vinyl aromaticmonomer; and (ii) a propoxylated allyl alcohol of the formula;

    CH.sub.2 ═CH-CH.sub.2 --(A).sub.n --OH

in which A is an oxypropylene group, and n, which is the average numberof oxypropylene groups in the propoxylated allyl alcohol, has a valueless than or equal to 2; and wherein the copolymer has a hydroxyl numberwithin the range of about 80 mg KOH/g to about 260 mg KOH/g, and anumber average molecular weight within the range of about 500 to about3500, and wherein the mole ratio of vinyl aromatic monomer topropoxylated allyl alcohol recurring units in the copolymer is withinthe range of about 50:50 to about 75:25.
 2. The unsaturated polyesterresin composition of claim 1 wherein the vinyl aromatic monomer isselected from the group consisting of styrene, alkyl-substitutedstyrenes, halogenated styrenes, and mixtures thereof.
 3. The unsaturatedpolyester resin composition of claim 2 wherein the vinyl aromaticmonomer is styrene.
 4. The unsaturated polyester resin composition ofclaim 1 wherein n has a value within the range of about 1.4 to about1.8.
 5. An unsaturated polyester resin composition which comprises thereaction product of:(a) an anhydride; (b) optionally, a glycol; and (c)a copolymer which comprises recurring units of:(i) styrene; and (ii) apropoxylated allyl alcohol of the formula:

    CH.sub.2 ═CH-CH.sub.2 --(A).sub.n --OH

in which A is an oxypropylene group, and n, which is the average numberof oxypropylene groups in the propoxylated allyl alcohol, has a valueless than or equal to 2; and wherein the copolymer has a hydroxyl numberwithin the range of about 80 mg KOH/g to about 260 mg KOH/g, and anumber average molecular weight within the range of about 500 to about3500, and wherein the mole ratio of styrene to propoxylated allylalcohol recurring units in the copolymer is within the range of about50:50 to about 75:25.
 6. The unsaturated polyester resin composition ofclaim 5 wherein n has a value within the range of about 1.4 to about1.8.